Kinetics and mechanism of the ligand substitution reaction between aquapentacyanoruthenate(II) and 4-cyanopyridine in the presence of anionic surfactant micelles

Abstract

The kinetics of ligand substitution between aquapentacyanoruthenate(II) ion, [Ru(CN) 5 H 2 O] 3-and 4-cyanopyridine (4-CNpy) has been investigated spectrophotometrically in the presence of anionic surfactant micelle, namely sodium dodecylsulphate (SDS) at 400 nm (k max of the intense yellow product [Ru(CN) 5 4-CNpy] 3-) under pseudo-first-order conditions using at least 10% excess of 4-CNpy over [Ru(CN) 5 H 2 O] 3-. The reaction was studied as a function of [Ru(CN) 5 H 2 O 3-], [4-CNpy], [SDS], pH, ionic strength and temperature, by varying each of these variables one at a time. The reaction exhibited overall second-order kinetics, being first order each in [4-CNpy] and [Ru(CN) 5 H 2 O 3-] over a wide concentration range.Variation of ionic strength of the medium had a significant negative effect on the rate. The SDS micelle, being negatively charged, does not reveal any regular effect except at or near its critical micelle concentration (c.m.c). The rate of reaction was measured at different temperatures, and the activation parameters were computed using Arrhenius and Eyring plots. A plausible mechanism consistent with the experimental results has been proposed.

Salt effects on the reactivity for ligand substitution reactions of [Ru(CN)5OH2]3−anion with two naphthalene substituted ligands (nitroso‐R‐salt and α‐nitroso‐β‐naphthol) in presence of Tetrapropylammonium bromide (Pr4NBr) and Sodium chloride (NaCl)

“…The above reaction is rapid and is complete shortly after mixing the two reagents. The solution showed a λ max at 310 nm, which was within the range reported in similar previous studies 33–36 …”

“…The solution showed a λ max at 310 nm, which was within the range reported in similar previous studies. [33][34][35][36] The rate of ligand exchange between the [Ru(CN) 5 OH 2 ] 3− and NRS or αNβN was measured at different molar concentrations and set temperatures in the presence of added salt at 525 nm. The initial molar concentration of the ligand was ten times excess to that of [Ru(CN) 5 OH 2 ] 3− , establishing a pseudo-first-order kinetic condition for each reaction.…”

“…11 Research of iron and ruthenium (II/III) complexes has gained substantial attention due to their wide applications in areas of medicine and industry. [12][13][14][15][16][17][18][19] More research studies have been done on the substitutional behavior and kinetics of Fe(II) complexes with heterocyclic incoming ligands in aqueous [20][21][22][23][24][25][26][27][28][29][30] and micellar [31][32][33][34][35][36] medium than their Ru(II) counterparts. [37][38][39][40] The replacement of cyanide coordinated to Ru(II) by nitrogen heterocyclic ligands in aqueous medium (via formation of [Ru(CN) 5 OH 2 ] 3− ) is extremely sluggish at room temperature and continues to proceed slowly even at higher temperatures.…”